Thank God it’s Friday is especially true this summer when you can visit a favorite venue or discover a new one for free.

A family of two adults and two children over age 4, for example, ordinarily would pay $112 to go to Plimoth Plantation and The Mayflower II. On Aug. 15, they pay nothing because of Free Fun Fridays, which begins Friday and runs through Aug. 29.

“People plan their summer around it,” said Blake Jordan, executive director of the Highland Street Foundation, which started and funds the program. “They tell us they can’t afford to go away, but they take Friday off and visit our venues. It’s a stayvacation.”

Plimoth Plantation, one of 67 participating museums, theaters, gardens and parks, expects about 8,000 people, based on last summer’s Free Fun Fridays attendance. Typically in August, 4,000 people visit over three days from Friday through Sunday.

“It’s one of our favorite days,” said Courtney Roy-Branigan, the plantation’s director of development. “For a lot of people, it’s their first time here and there’s a kind of curiosity. There are a lot of kids, and our staff are asked questions they don’t normally hear.”

To accommodate so many people, Plimoth Plantation adds shade and misting tents, extra benches, hands-on activities and a shuttle bus from overflow parking at Home Depot on Long Pond Road.

Started in 2008 as part of the foundation’s 20th anniversary celebration, Free Fun Fridays originally had just 10 sites and 60,000 visitors. Last year, 60 sites received 165,000 visitors.

“After last year, I thought there’s no way there are more venues,” said Jordan, who added six new sites for this summer. “That’s what’s so great about where we live. There are so many unbelievable resources.”

Free Fun Fridays is an incentive to explore smaller, less well known and unusual places, such as the eight-year-old Museum of Russian Icons in Clinton, near Worcester. Typically about 50 people a day visit; last year on Free Fun Fridays, about 5,000 visited.

“People say, ‘I didn’t know about that place’ or ‘I drive by, but never stop in. Today I did and I will go back,’” Jordan said.

The free admissions are spread throughout the summer, with about five to seven locations from Cape Cod to the Berkshires free each Friday. The Highland Street Foundation, which spends $650,000 on the program, gives grants to each organization to cover the lost admission fees.

The new venues this year are the MIT Museum, Sandwich Glass Museum, Cape Cod Maritime Museum, Falmouth Museums on the Green, Tower Hill Botanical Gardens, and Historic Deerfield.

If you want to get started on opening day, visit the Sports Museum in Boston and save $30 for two adults and two children age 10, or visit Franklin Park Zoo and save $59.80 for two adults and two children ages 2 and up.

To make a longer trip worthwhile, combine two free sites. In the Greater Worcester area on Aug. 15, visits are free at both the Museum of Russian Icons and the Fitchburg Art Museum.

In addition to having North America’s largest collection of Russian Orthodox icons (hand-painted images of holy people or events), the museum has the exhibit “Darker Shades of Red: Soviet Propaganda Art from the Cold War Era.” It showcases Communist posters, banners and statuettes that promoted Soviet Union ideology from post World War II to 1990 and that caricatured the United States and Western Europe. Inside, its Russian Tea Room visitors dine on tea and authentic Russian chocolate, biscuits and snacks beneath an LED ceiling light show.

The Fitchburg Art Museum has galleries of ancient Egyptian, Greek, Etruscan, Roman and African art, as well as a significant photography collection.

While Commonwealth Shakespeare performs for free each summer on the Boston Common, this year’s production of “Twelfth Night” will be preceded by Free Fun Fridays activities for kids, as well as a free concert sponsored by the New England Conservatory.

If you’re on Cape Cod on July Fourth and want an addition to parades, barbecues and the beach, take advantage of free admission at Heritage Museum & Gardens, Falmouth Museums on the Green and the Edward Gorey House in Yarmouthport.

One of the most popular free opportunities is the ferry rides to Georges and Spectacle islands on Aug. 8, which can be combined with free carousel rides nearby on the Rose Kennedy Greenway. Arrive early, since the roughly 5,000 spaces on the boats are expected to fill by noon.

So, go out, have fun and be glad it’s Friday.

For information, go to www.highlandstreet.org

Jody Feinberg may be reached at jfeinberg@ledger.com or follow her on Twitter @JodyF_Ledger.